* What is the purpose of EXTENT_PAGE_MAPPED
@ 2017-10-24 10:47 Goldwyn Rodrigues
2017-10-27 4:17 ` Liu Bo
0 siblings, 1 reply; 6+ messages in thread
From: Goldwyn Rodrigues @ 2017-10-24 10:47 UTC (permalink / raw)
To: linux-btrfs
EXTENT_PAGE_MAPPED gets set in set_page_extent_mapped(), but I don't see
it being cross checked anytime. What is the purpose of setting it?
--
Goldwyn
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: What is the purpose of EXTENT_PAGE_MAPPED
2017-10-24 10:47 What is the purpose of EXTENT_PAGE_MAPPED Goldwyn Rodrigues
@ 2017-10-27 4:17 ` Liu Bo
2017-10-30 13:21 ` Nikolay Borisov
0 siblings, 1 reply; 6+ messages in thread
From: Liu Bo @ 2017-10-27 4:17 UTC (permalink / raw)
To: Goldwyn Rodrigues; +Cc: linux-btrfs
On Tue, Oct 24, 2017 at 05:47:11AM -0500, Goldwyn Rodrigues wrote:
>
> EXTENT_PAGE_MAPPED gets set in set_page_extent_mapped(), but I don't see
> it being cross checked anytime. What is the purpose of setting it?
Please check commit d1310b2e0cd98eb1348553e69b73827b436dca7b, it was
used to differentiate page for metadata and for data, but I think
currently it's just a piece of legacy code.
-liubo
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: What is the purpose of EXTENT_PAGE_MAPPED
2017-10-27 4:17 ` Liu Bo
@ 2017-10-30 13:21 ` Nikolay Borisov
2017-10-30 13:55 ` David Sterba
0 siblings, 1 reply; 6+ messages in thread
From: Nikolay Borisov @ 2017-10-30 13:21 UTC (permalink / raw)
To: bo.li.liu, Goldwyn Rodrigues; +Cc: linux-btrfs
On 27.10.2017 07:17, Liu Bo wrote:
> On Tue, Oct 24, 2017 at 05:47:11AM -0500, Goldwyn Rodrigues wrote:
>>
>> EXTENT_PAGE_MAPPED gets set in set_page_extent_mapped(), but I don't see
>> it being cross checked anytime. What is the purpose of setting it?
>
> Please check commit d1310b2e0cd98eb1348553e69b73827b436dca7b, it was
> used to differentiate page for metadata and for data, but I think
> currently it's just a piece of legacy code.
Be that as it may - is there any reason why we are keeping this and can
it be killed off?
>
> -liubo
> --
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: What is the purpose of EXTENT_PAGE_MAPPED
2017-10-30 13:21 ` Nikolay Borisov
@ 2017-10-30 13:55 ` David Sterba
2017-10-30 14:01 ` Nikolay Borisov
0 siblings, 1 reply; 6+ messages in thread
From: David Sterba @ 2017-10-30 13:55 UTC (permalink / raw)
To: Nikolay Borisov; +Cc: bo.li.liu, Goldwyn Rodrigues, linux-btrfs
On Mon, Oct 30, 2017 at 03:21:51PM +0200, Nikolay Borisov wrote:
>
>
> On 27.10.2017 07:17, Liu Bo wrote:
> > On Tue, Oct 24, 2017 at 05:47:11AM -0500, Goldwyn Rodrigues wrote:
> >>
> >> EXTENT_PAGE_MAPPED gets set in set_page_extent_mapped(), but I don't see
> >> it being cross checked anytime. What is the purpose of setting it?
> >
> > Please check commit d1310b2e0cd98eb1348553e69b73827b436dca7b, it was
> > used to differentiate page for metadata and for data, but I think
> > currently it's just a piece of legacy code.
>
> Be that as it may - is there any reason why we are keeping this and can
> it be killed off?
Are we're talking about EXTENT_PAGE_PRIVATE? There's no
EXTENT_PAGE_MAPPED. There's some control dependency on the page private
bit and the value, so we should be careful and replace the function with
an assert (or a BUG_ON if it's a must-not-happen state). The page->private
points to an extent buffer, and if it's always an eb, then the
EXTENT_PAGE_PRIVATE is unused.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: What is the purpose of EXTENT_PAGE_MAPPED
2017-10-30 13:55 ` David Sterba
@ 2017-10-30 14:01 ` Nikolay Borisov
2017-10-30 14:04 ` Goldwyn Rodrigues
0 siblings, 1 reply; 6+ messages in thread
From: Nikolay Borisov @ 2017-10-30 14:01 UTC (permalink / raw)
To: dsterba, bo.li.liu, Goldwyn Rodrigues, linux-btrfs
On 30.10.2017 15:55, David Sterba wrote:
> On Mon, Oct 30, 2017 at 03:21:51PM +0200, Nikolay Borisov wrote:
>>
>>
>> On 27.10.2017 07:17, Liu Bo wrote:
>>> On Tue, Oct 24, 2017 at 05:47:11AM -0500, Goldwyn Rodrigues wrote:
>>>>
>>>> EXTENT_PAGE_MAPPED gets set in set_page_extent_mapped(), but I don't see
>>>> it being cross checked anytime. What is the purpose of setting it?
>>>
>>> Please check commit d1310b2e0cd98eb1348553e69b73827b436dca7b, it was
>>> used to differentiate page for metadata and for data, but I think
>>> currently it's just a piece of legacy code.
>>
>> Be that as it may - is there any reason why we are keeping this and can
>> it be killed off?
>
> Are we're talking about EXTENT_PAGE_PRIVATE? There's no
> EXTENT_PAGE_MAPPED. There's some control dependency on the page private
> bit and the value, so we should be careful and replace the function with
> an assert (or a BUG_ON if it's a must-not-happen state). The page->private
> points to an extent buffer, and if it's always an eb, then the
>EXTENT_PAGE_PRIVATE is unused.
I guess I meant do we actually need: set_page_extent_mapped and all the
jazz happening in it or is it a leftover (which I believe it is) ?
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: What is the purpose of EXTENT_PAGE_MAPPED
2017-10-30 14:01 ` Nikolay Borisov
@ 2017-10-30 14:04 ` Goldwyn Rodrigues
0 siblings, 0 replies; 6+ messages in thread
From: Goldwyn Rodrigues @ 2017-10-30 14:04 UTC (permalink / raw)
To: Nikolay Borisov, dsterba, bo.li.liu, linux-btrfs
On 10/30/2017 09:01 AM, Nikolay Borisov wrote:
>
>
> On 30.10.2017 15:55, David Sterba wrote:
>> On Mon, Oct 30, 2017 at 03:21:51PM +0200, Nikolay Borisov wrote:
>>>
>>>
>>> On 27.10.2017 07:17, Liu Bo wrote:
>>>> On Tue, Oct 24, 2017 at 05:47:11AM -0500, Goldwyn Rodrigues wrote:
>>>>>
>>>>> EXTENT_PAGE_MAPPED gets set in set_page_extent_mapped(), but I don't see
>>>>> it being cross checked anytime. What is the purpose of setting it?
>>>>
>>>> Please check commit d1310b2e0cd98eb1348553e69b73827b436dca7b, it was
>>>> used to differentiate page for metadata and for data, but I think
>>>> currently it's just a piece of legacy code.
>>>
>>> Be that as it may - is there any reason why we are keeping this and can
>>> it be killed off?
>>
>> Are we're talking about EXTENT_PAGE_PRIVATE? There's no
>> EXTENT_PAGE_MAPPED. There's some control dependency on the page private
>> bit and the value, so we should be careful and replace the function with
>> an assert (or a BUG_ON if it's a must-not-happen state). The page->private
>> points to an extent buffer, and if it's always an eb, then the
>> EXTENT_PAGE_PRIVATE is unused.
>
> I guess I meant do we actually need: set_page_extent_mapped and all the
> jazz happening in it or is it a leftover (which I believe it is) ?
>
We definitely need set_page_extent_mapped() to set the page private for
the lowers layers to handle I/O, primarily writebacks. However, we may
not need EXTENT_PAGE_PRIVATE (yes, I got it wrong the first time). I am
still reading on this though.
--
Goldwyn
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2017-10-30 14:04 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-10-24 10:47 What is the purpose of EXTENT_PAGE_MAPPED Goldwyn Rodrigues
2017-10-27 4:17 ` Liu Bo
2017-10-30 13:21 ` Nikolay Borisov
2017-10-30 13:55 ` David Sterba
2017-10-30 14:01 ` Nikolay Borisov
2017-10-30 14:04 ` Goldwyn Rodrigues
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